Security researchers have identified two critical vulnerabilities in the widely-used vBulletin forum software, assigned as CVE-2025-48827 and CVE-2025-48828. These high-severity flaws, both rated 9.0 on the CVSS scale, pose significant risks to forum administrators worldwide, with one vulnerability already being actively exploited in the wild.
Technical Assessment of the Vulnerabilities
The discovered security flaws affect vBulletin versions ranging from 5.0.0 to 5.7.5 and 6.0.0 to 6.0.3 running on PHP 8.1 and newer. Security researcher Egidio Romano (EgiX) identified that the core issue stems from improper implementation of PHP Reflection API, enabling attackers to bypass security mechanisms during method calls. This implementation flaw creates a critical attack vector that could potentially lead to remote code execution.
Exploitation Methodology and Impact
The vulnerabilities center around the replaceAdTemplate method, which can be manipulated through carefully crafted URL requests to inject malicious code. What makes these vulnerabilities particularly dangerous is their ability to circumvent built-in security filters through PHP variable manipulation, potentially granting attackers remote server access with command execution privileges.
Active Exploitation and Threat Intelligence
Security researcher Ryan Dewhurst has documented active exploitation attempts of CVE-2025-48827 in the wild. Honeypot logs have revealed suspicious requests targeting the ajax/api/ad/replaceAdTemplate endpoint, with at least one threat actor from Poland attempting to deploy PHP backdoors for system compromise. This real-world exploitation emphasizes the immediate need for protective measures.
Security Patches and Mitigation Strategies
The vBulletin development team has released security patches through Patch Level 1 for version 6.* and Patch Level 3 for version 5.7.5. System administrators are strongly advised to implement these security updates immediately, particularly for internet-facing forums. Additional recommended security measures include:
• Implementing robust logging and monitoring systems
• Regularly reviewing server access logs for suspicious activities
• Deploying Web Application Firewalls (WAF) with updated rule sets
• Conducting regular security audits of forum installations
While no confirmed cases of successful remote access exploitation have been reported, the public availability of exploit code and the critical nature of these vulnerabilities demand immediate attention. Organizations running vBulletin forums should prioritize these security updates and implement comprehensive monitoring solutions to detect and prevent potential exploitation attempts. The window for preventive action is crucial, as threat actors are actively scanning for vulnerable installations.
